Statistics obtained from the Fire Marshall Office of the State of Maryland show that kitchens are the most frequent areas of residential fire origin. Of the kitchen fires reported in 1996, close to 75% of them were accidents from cooking. All cooking appliances other than stove-top burners in the kitchen are governed either by temperature or time or both. This exception has made the stove-top burners a major fire hazard in a residential kitchen. Many fires are initiated there due to negligence wherein a burner is accidently left on with food in a utensil. The content of the utensil eventually ignites when the dried food is held at cooking temperatures for a prolonged period after all liquids have evaporated.
Efforts have been made in the past to address this issue. Examples of some recently patented safety devices designed for stove-top burners are: 1. a switch that allows a burner to be turned on only when there is a utensil placed on it (U.S. Pat. No. 4,577,181); 2. a motion detector installed in the stove appliance that automatically reduces or turns off power to the stove if no movement is detected in the proximity within a predetermined length of time (U.S. Pat. Nos. 4,775,913; 5,717,188; 5,380,985); 3. an automated fire extinguisher installed above a stove (U.S. Pat. No. 4,483,314; 5,490,566 and others); and 4. a combination sensor installed in the center of an electric hotplate that senses the presence of a utensil, measures its temperature and cuts off electrical supply to the hotplate when temperature reaches a predetermined value (U.S. Pat. No. 5,294,779). These designs each only address part of the problem and do not provide a complete solution. For example, design 1 will not prevent overheating conditions and design 2 cannot be used in the user's absence for prolonged boiling or steaming of food. Design 3 requires extensive modification around the stove area and may be falsely triggered in some cooking processes using high heat, such as frying. Regarding the aspect of providing a positive power shut-off when a critical utensil temperature is reached in cooking, this invention shares the same objective as design 4. However, a senor switch with a fixed temperature threshold as suggested by design 4 cannot be used in all cooking situations. When used in high heat applications, such as during frying, the hotplate could be turned off prematurely.
Other efforts in the U.S. and elsewhere to regulate the stove-tops include the controlling of burner settings or on-off cycles according to the temperature of the cooking utensil placed on it (U.S. Pat. Nos. 4,499,368; 4,587,406; 4,692,596; 4,714,822 and others). Temperature sensitive switches are either incorporated directly into stove-top burners or attached to utensils to regulate burner power. Some designs include both a timer and temperature control. They provide some amount of safety measure in that either temperature or time is controlled during the cooking period. They, however, do not eliminate fire hazards. In some overheating conditions, power could still be cyclically supplied to the burner. One of the designs uses microprocessor control and the rate of utensil temperature change information to prevent boil-dry conditions under special usage settings or a burner from being energized while unoccupied. These efforts all involve costly and elaborate designs to automate certain cooking processes and not to address any specific fire safety issues. Furthermore, complicated usage instructions limit their acceptance.
Accordingly, it is an object of this invention to provide stove-top burners with a higher standard of safety that will dramatically reduce the chance of kitchen fires due to cooking.